Author Daniel Blaustein-Rejto did a pretty nice job on an article on farm scale biochar for Acres magazine. It's in the October 2014 issue: "Playing With Fire - Creating, Using Biochar for Improved Soil." Many of the pictures in the article are from technologies featured on this website. So thanks everyone, for contributing your pictures and stories. More and more people are learning about these small scale, clean biochar technologies, and using them to improve their soils.
Check out this very interesting page on Conical Pot Stands for stoves. There are a variety of construction tools here for laying out cones and lots of ideas for how to use them in various combustion devices. Hours of fun!
How much storage does your device have? No, not your phone, your biochar kiln! What if you could remove biochar from the bottom of your kiln and keep going? I had the idea of setting my cone kiln on top of a 55 gallon drum and letting the charcoal fall into the drum. I even made some sketches of the idea, but have not gotten around to making one yet. Then I get an email from Larry Peceniak and he has done it. And very nicely too. I really like his idea of welding the cone onto the lid. That makes it super easy to seal. Here's what he says about it:
I had a hole cut in the removable lid of a 55 gallon drum the size of the bottom of the cone kiln. I then had the bottom of the kiln welded to this lid. In the bottom of the kiln I put a piece of 2”x1” fence cut slightly larger than the bottom of the kiln. This holds up the stock to be charred. I put the "kiln lid "on a empty 55 gallon drum, and began to char my orchard prunings from this winter. When the kiln started to get full, I just took a stick and moved the char around and it fell down into the bottom of the 55 gallon drum. When I got tired I just waited for all the stock to char, took the “kiln lid” off, and put a solid lid on the drum to stop the char from going to ash. This was my first burn so I’ll let you know how the char turns out. I think I’m going to try to find a 14” barbecue grate to weld in the bottom of the kiln instead of the fence. However, I was really pleased with the way the kiln performed.
This is very slick and I am going to make one as soon as fire season is over. Can't burn anything right now in Oregon. Here's the picture:
Larry Peceniak has caught the cone kiln bug and has made several versions out of lightweight sheet steel:
I used 2’x3’ 30 gauge galvanized steel for duct work from Home Depot. The metal is pretty flimsy, but it gets the job done.
Looks like he uses pop rivets to hold it together. We'll have to get a report from him later on how long this lightweight materal lasts, but for now he's having a great time. He says:
The first char with the new kiln was outstanding. I charred 15 gallons of split 2x10 pine from a home construction site in about 2 hours while sitting on my patio enjoying the fire! The cone kiln I can actually set in a patio fire pit that I bought and it works great. Now I can sit on my patio, do a char, and enjoy the fire while I’m just sitting with my wife enjoying a glass of wine.
Kamal Rashid, CEO at Zanjabil Gardens in Pembroke Township, Illinois, has made a giant cone kiln. Last month he completed his first full test burn in the kiln, which has a 59" top diameter, a 24" bottom diameter, and is 24" high. The kiln made 133 gallons of biochar (17.7 cu ft) in about 4 hours, using cordwood. Kamal reports that it took 30 gallons of water to quench the kiln.
Kamal is also an officer of the Pembroke Farming Family Association, and he helps with technical assistance to other farmers. Kamal is very happy with the cone kiln, which was fabricated by a local community college welding class. You can bet he will be helping other small farmers in his area get started with making and using biochar. Here are some of his pictures:
Here are some pictures of Michael's Cone Kiln at the Simi Community Garden. Notice that it has a bottom. This helps conserve the quenching water. The handles are very nice too. Most impressive is the 3 cones operating at once!
I had my friend Kevin, who operates a small welding shop, make my first cone kiln based on the dimensions of the 100 cm Moki kiln.
Here are quick specs on the cone kiln if you want to try making your own: It was made from a 4x8 sheet of 16 gauge steel with 3/8" rod welded around top and bottom rims for stability. Top diameter is 43". Bottom diameter is 16" and height is 16". It is open on the bottom. That's it. My welder had a heck of a time bending the steel to make the seam weld. Needs a couple of strong guys or preferentially a differential slip roller to roll the form into shape. You could also make it from lighter weight steel.
My cone kiln:
Here are quick specs on the cone kiln if you want to try making your own: It was made from a 4x8 sheet of 14 16 gauge steel with 3/8" rod welded around top and bottom rims for stability. Top diameter is 43". Bottom diameter is 16" and height is 16". It is open on the bottom so you just roll it away when you are done. That's it. My welder had a heck of a time bending the steel to make the seam weld. Needs a couple of strong guys or preferentially a differential slip roller to roll the form into shape. You could also make it from lighter weight steel. - See more at: http://www.greenyourhead.com/cone-kiln/#sthash.4k5ZWqI8.dpuf
If you have been around biochar for awhile, you know that there are many types of biochar with very different characteristics. Biochar characteristics differ depending on the feedstock used, processing temperature and exposure to oxygen. Things to look for in biochar properties are pH, surface area and porosity, ash content, volatile matter content, and the "fixed" carbon content. Fixed carbon refers to the degree that the carbon has been converted to stable benzene rings that do not degrade easily.
Biochar made in the cone kiln from pine, black locust and bamboo, compared favorably with biochar made at fairly high temperatures (600 C) in a retort placed inside a laboratory oven. The cone kiln biochar has as much fixed carbon and surface area as the retort char. The cone kiln char had higher pore volume than the retort chars, and superior water holding capacity. The reason for the difference is that the cone kiln char carbonized more quickly than the retort char (the heat is transferred more quickly since it does not have to pass through a metal retort wall), shrinking less in the process, and maintaining more pore spaces inside.
Other findings from the paper include the efficiency of the cone kiln process: For red pine, about 14% of the feedstock mass (dry basis) was converted to biochar, with about 24% of the carbon retained. Values were higher for black locust and bamboo. The pH was higher in the cone kiln biochar because of the ash produced. This can be altered by rinsing the biochar, or composting with other materials if the high pH is not desired.
The researchers concluded that the cone kiln biochar is "suitable for amendment that would enhance water-holding capacity of soil and neutralize acidic soil."
When I first encountered the Cone Kiln, I thought it worked on the principle of TLUD - Top-Lit Up-Draft gasifier. But I was wrong.
With a TLUD, the fuel is loaded all at once into a container and lit on the top. Air comes in from the bottom and a flame burns on the top. Slowly, the top fire heats biomass below it, and it gasifies. The flame burns the gas emitting from hot biomass below. When all the gas is gone, you are left with only charcoal and the flame goes out. Read all about TLUDs at the Dr. TLUD site.
With an Open Fire Kiln, a small fire is started in the bottom of the container. There is no air coming up from the bottom; instead all the air comes down from the top and swirls over the top of the burning biomass, feeding the flame. Like this:
This picture shows the cone kiln when it is almost done. The black sticks in the bottom are charcoal. As you add new layers of wood on top of the burning coals, the new wood excludes air from the layers below. Those layers stay hot, and continue to emit gas, but the charcoal does not burn. When the kiln is full, quench with water. That is how an Open Fire Kiln works.
The Open Fire Kiln is an "autothermal" process, just like the TLUD. An autothermal kiln burns part of the feedstock material to heat the rest of the material and turn it into char.
An externally heated kiln uses an "allothermal" process. It provides a separate source of heat to heat an enclosed chamber or retort. Heat must be transferred through the walls of the retort to heat the biomass inside. The biomass emits gas that should be burned to add heat to the process.
Backyard Biochar This site has descriptions of my experiments with Flame Cap Kilns. I also report on work by others.
US Biochar Initiative I am on the advisory board of the USBI. We are sponsoring the 5th North American Biochar Symposium in Corvallis, Oregon - August 22-25, 2016
Illinois Valley Forest Collaborative I've been involved with the group in my hometown for several years. We are working with the US Forest Service on hazardous fuels and small diameter timber sales. Biochar is a part of what we do.
Umpqua Biochar Education Team (UBET) I am working with UBET on a Conservation Innovation Grant from the USDA-NRCS. We are helping small farmers learn how to make biochar and use it to manage manure and make premium compost.